1. Field of the Invention
The present invention relates to a method for plasma control and an apparatus for plasma control used in plasma CVD, plasma RIE, and spattering.
2. Description of the Related Art
Plasma processing is categorized to various technologies such as plasma CVD, plasma RIE, spattering and ion plating, but any way in the all these technologies an object to be processed is placed in a processing chamber and a type of plasma is generated, thus the object is subjected to film forming or etching by the action of ion or electron.
FIGS. 1A and 1B are schematic diagrams for illustrating conventional plasma processing equipments, FIG. 1A shows a parallel flat plate type, and FIG. 1B shows ECR type equipments.
The parallel flat plate type equipment comprises a processing chamber 1 in which the object 4 to be processed such as wafer is placed, top and bottom electrodes 5 and 6 provided facing each other in the processing chamber 1, and a DC bias 2 and high frequency bias 3 for applying voltage on the bottom electrode 6.
For processing using the parallel flat plate type plasma processing equipment, a gas (not shown) is introduced in the processing chamber 1, and high frequency bias 3 of, for example, 13.56 MHz is applied to generate plasma 7 in a space between the top electrode 5 and the bottom electrode 6, and thus, for example, a film is formed on the surface of the object 4.
Plasma 7 in the processing chamber 1 is controlled by electric field perpendicular to the surface of the object 4 and flow of the gas to maintain the plasma density uniform.
The ECR type plasma processing equipment shown in FIG. 1B comprises a processing chamber 11 in which the object 10 to be processed is placed, a wave guide 11a for feeding microwave into the processing chamber 11, and coils 12 for generating magnetic field.
For operating the ECR type plasma processing equipment, a gas is introduced into the processing chamber 11 and microwave with a frequency of, for example, 2.45 GHz is fed to cause discharging, and the rotation of electrons which are being rotated by applying magnetic field from the coils 12 resonates with the frequency of microwave to generates high performance plasma 13.
The plasma 13 in the processing chamber 1 is controlled by prescribed bias and gas flow to process the object 10.
In any plasma processing equipment for proper processing, ion or electron is controlled to be projected perpendicular to the surface of the object.
Therefore, the quality of processing in the direction perpendicular to the surface of the object, for example, film thickness and etching depth, can be controlled, but the quality in the direction other than perpendicular direction cannot be controlled, and these equipments are not suitable for processing of the object with complex structure.
For example, when a taper is to be provided at a trench and a oxide film with desired thickness is to be formed on the inside surface of the trench on a semiconductor element, a conventional plasma processing equipment cannot control such processing, this disadvantage of the conventional equipment has been a serious problem for processing objects with complex structure.